[GRASS-user] Polar projection
Jón Eiríksson
jeir at hi.is
Sat Jan 2 03:52:05 PST 2021
Dear Ken,
I am afraid I do have the same problem, - the command does not make a
grid to the pole. Should have tested before responding, sorry. So I
think you should proceed with a bug report,
Jon
On 1 Jan 2021, at 17:12, Ken Mankoff wrote:
> Hi Jón,
>
> I work regularly in EPSG:3413, but the same issue applies. "d.grid -g
> 1:0" doesn't make a grid to the pole. Does it for you? I'd like to
> submit a bug report as per the suggestion from Markus, but am not sure
> what the bug is if this command works for you when the pole is
> included in the view.
>
> -k.
>
> On 2020-12-31 at 09:23 -08, Jón Eiríksson <jeir at hi.is> wrote...
>> This has worked for me:
>>
>> (Thu Dec 31 17:22:11 2020)
>> g.proj -p
>> -PROJ_INFO-------------------------------------------------
>> name : Stereographic
>> proj : stere
>> datum : wgs84
>> ellps : wgs84
>> lat_0 : 90
>> lat_ts : 70
>> lon_0 : -45
>> k : 1
>> x_0 : 0
>> y_0 : 0
>> no_defs : defined
>> towgs84 : 0.000,0.000,0.000
>> -PROJ_EPSG-------------------------------------------------
>> epsg : 3413
>> -PROJ_UNITS------------------------------------------------
>> unit : meter
>> units : meters
>> meters : 1
>> (Thu Dec 31 17:22:11 2020) Command finished (0 sec)
>>
>> Jon
>>
>>
>>
>>
>> On 31 Dec 2020, at 16:26, Markus Neteler wrote:
>>
>>> Hi Ken,
>>>
>>> On Thu, Dec 31, 2020 at 3:06 AM Ken Mankoff <mankoff at gmail.com>
>>> wrote:
>>>>
>>>> Dear GRASS List,
>>>>
>>>> Can someone suggest what setup to use (EPSG code? proj4 code?) to
>>>> have the projection centered on the N. pole? I'm looking to create
>>>> a graphic similar to this image in the Raster Gallery:
>>>> https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgrass.osgeo.org%2F%2Fimages%2Fgallery%2Fraster%2Fday_on_earth_N.png&data=04%7C01%7Cjeir%40hi.is%7Cbab065ba5fa94867219a08d8ae786727%7C09fa5f0e211846568529677ed8fdbe78%7C0%7C0%7C637451179441104707%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=zcVbgCptTcrREvuVucAfEWdb%2BPH2Qsl6DktIkru94jE%3D&reserved=0
>>>>
>>>> If I set up a polar projection based on
>>>> https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fspatialreference.org%2Fref%2Fsr-org%2F8243%2F&data=04%7C01%7Cjeir%40hi.is%7Cbab065ba5fa94867219a08d8ae786727%7C09fa5f0e211846568529677ed8fdbe78%7C0%7C0%7C637451179441104707%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=QrsQH1MA6ehd%2BcPpLwwQ6190ki6shHnr7UptJsF50EU%3D&reserved=0
>>>> using:
>>>>
>>>> grass -c ./G
>>>> g.proj -c proj4="+proj=stere +lat_0=90 +lat_ts=45 +lon_0=-170 +k=1
>>>> +x_0=0 +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_defs"
>>>>
>>>> Things mostly work, but
>>>>
>>>> d.grid -g 1:0 color=red
>>>>
>>>> does not show latitude lines on most of the graphic (see attached).
>>>
>>> I managed to generate it with
>>>
>>> Preparation of a 10 degree grid:
>>>
>>> # EPSG:4326
>>> GRASS :~ > g.region -dp
>>> projection: 3 (Latitude-Longitude)
>>> zone: 0
>>> datum: wgs84
>>> ellipsoid: wgs84
>>> north: 90N
>>> south: 90S
>>> west: 180W
>>> east: 180E
>>> nsres: 1
>>> ewres: 1
>>> rows: 180
>>> cols: 360
>>> cells: 64800
>>> GRASS :~ > v.mkgrid grid=36,18 map=grid_10deg
>>> # download "Natural Earth I with Shaded Relief, Water, and
>>> Drainages"
>>> from
>>> https://eur02.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.naturalearthdata.com%2Fdownloads%2F10m-raster-data%2F10m-natural-earth-1%2F&data=04%7C01%7Cjeir%40hi.is%7Cbab065ba5fa94867219a08d8ae786727%7C09fa5f0e211846568529677ed8fdbe78%7C0%7C0%7C637451179441104707%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=BmlSMFy8mUpdUQxbZw10dM7Rzzq4Vztpc33Ha8dx75M%3D&reserved=0
>>> GRASS :~ > r.import in=NE1_HR_LC_SR_W_DR.tif
>>> output=natural_earth_global_landcover
>>> GRASS :~ > g.region raster=natural_earth_global_landcover.1
>>> GRASS :~ > r.composite r=natural_earth_global_landcover.1
>>> g=natural_earth_global_landcover.2
>>> b=natural_earth_global_landcover.3
>>> out=natural_earth_global_landcover.rgb
>>> GRASS :~ > exit
>>>
>>> # WGS 84 / Arctic Polar Stereographic
>>> https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fepsg.io%2F3995&data=04%7C01%7Cjeir%40hi.is%7Cbab065ba5fa94867219a08d8ae786727%7C09fa5f0e211846568529677ed8fdbe78%7C0%7C0%7C637451179441104707%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=67g63WlKT3zJfzmTuPxNAciU9Uq65N%2F6ypc%2FpjntWT8%3D&reserved=0
>>> grass78 -c epsg:3995 ~/grassdata/arctic_polar_stereographic
>>> GRASS :~ > g.proj -w
>>> PROJCS["WGS 84 / Arctic Polar Stereographic",
>>> GEOGCS["WGS 84",
>>> DATUM["WGS_1984",
>>> SPHEROID["WGS 84",6378137,298.257223563,
>>> AUTHORITY["EPSG","7030"]],
>>> AUTHORITY["EPSG","6326"]],
>>> PRIMEM["Greenwich",0,
>>> AUTHORITY["EPSG","8901"]],
>>> UNIT["degree",0.0174532925199433,
>>> AUTHORITY["EPSG","9122"]],
>>> AUTHORITY["EPSG","4326"]],
>>> PROJECTION["Polar_Stereographic"],
>>> PARAMETER["latitude_of_origin",71],
>>> PARAMETER["central_meridian",0],
>>> PARAMETER["false_easting",0],
>>> PARAMETER["false_northing",0],
>>> UNIT["metre",1,
>>> AUTHORITY["EPSG","9001"]],
>>> AXIS["Easting",SOUTH],
>>> AXIS["Northing",SOUTH],
>>> AUTHORITY["EPSG","3995"]]
>>>
>>> GRASS :~ > g.region n=2930000 s=-2500000 w=-4250000 e=4310000
>>> nsres=10000 ewres=10000 -p
>>> GRASS :~ > v.proj location=latlong_wgs84 mapset=PERMANENT
>>> input=grid_10deg
>>> GRASS :~ > r.proj location=latlong_wgs84 mapset=PERMANENT
>>> input=natural_earth_global_landcover.rgb
>>> GRASS :~ > d.mon wx0
>>> GRASS :~ > d.rast natural_earth_global_landcover.rgb
>>> GRASS :~ > d.vect grid_10deg type=boundary
>>>
>>> The resulting map looks as attached (hope I didn't forget to copy a
>>> command here).
>>> Indeed, d.grid doesn't looks as expected
>>>
>>> GRASS :~ > d.grid 10 -w
>>> .. is incomplete. Worth a bug report, IMO.
>>>
>>> Cheers,
>>> Markus
>>>
>>> -- Markus Neteler, PhD
>>> https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.mundialis.de%2F&data=04%7C01%7Cjeir%40hi.is%7Cbab065ba5fa94867219a08d8ae786727%7C09fa5f0e211846568529677ed8fdbe78%7C0%7C0%7C637451179441104707%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=3v7mHEoyzVax4Wlfu6M3qLl%2FwIUpAeek4il6yjc8hNI%3D&reserved=0
>>> - free data with free software
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